Carburetor



April 27 A. J. LAIRD GARBURETOR Filed Sept. 19, 922

2 Sheets-Sheet 1 WITNEKES'.

Patented Apr. 27, 192%.

lCE.

ARGHIBALD JARVIE LAIRD, OF GLASGOW, SCOTLAND.

CARBURETOR.

Application filed September 19, 1922. Serial No. 589,189.

To all whom it may concern:

Be it known that I, ARoHInALD JARVIE LAIRD, of 1 Smith Street west, Glasgow, Scotland, a subject of the King of Great Britain, have invented certain new and useful Improvements in and Relatin to Carburetors, of which the following is a speci fication.

My invention relates to spraying and atomizing devices for liquid fuel, and its ob- W ject is to provide an improved device of this kind particularly for use as a carburetor for internal combustion engines.

To the attainment of this object the in vention consists of a carburetor, comprising a casing, means in the casing forming separate passages, leading to a common outlet, for the supply of separate streams of primary gaseous mixture and air directed across one another at the outlets of said passages, a member serving as a throttle valve to vary the area of the common outlet of the primary gaseous mixture and air and as an impinging and spreading surface to direct the said mixture across the surrounding air passage, and means, movable with the said member, whereby the area of the air passage and the amount of primary gaseous mixture can be varied simultaneously with the area of the said common outlet. By directing the gaseous mixture and air in streams which cross one another a thorough comminution and atomization of the fuel is obtained.

The mixture passage may be variable independently of the .air passage to enable the proportion of fuel and air to be altered for each and every position of the control means, in order to give a strength of mixture suitable to prevailing conditions and a rich starting mixture, each and every such variation of mixture being compensated by the aforesaid means.

. The invention also consists in the novel arrangement and combination of parts as hereinafter described and claimed. A form of carburetor embodying the invention is illustrated by way of example the accompanying drawing, whereon:

Fig. lis an outside elevation and Fig. 2 a part sectional elevation of one form of carburetor embodying the invention, shown with the throttle closed. Fig. 3 is a fragmentary sectional elevation with the throttle shown fully open.

Fig. l shows certain details of construcconstruction and communicating with a fuel nozzle 8 arranged co-axial with the casing and pro ecting into 1ts lower open end in which a V e-nturi tube 9 is slidably mounted over the fuel nozzle.

As illustrated by Figs. 1-3, the upper part of the tubular casing 6 is enlarged and a a sleeve 10 is slidably mounted in the bore of the casing so as to provide an-inner passage 11, through the sleeve, for the supply of fuel, from the nozzle 8, and air which enters the lower end of the casing, and an outer concentric passage 12 for the supply of air which enters through openings 13 in the side wall of the enlarged part of the casing.

At its upper end the sleeve member 10 is flared outwardly andconstitutes a valve adapt-ed to co-act with a seat 14: formed integral with a flanged member 15 fastened by a ring clip 16 to the casing 6 and serving as a means for securing the carburetor to the induction pipe of an internal combustion engine. The flared end of the sleeve member has its bore enlarged (see Fig. 4:) to provide an inner shoulder 1'? on which rests a spider 8 internally screw threaded at 19 to receive a tapered plug 20 and cut away at the sides to provide an outlet from the sleeve 10 when the plug is in place. The head 21 of the plug which is slidable with the sleeve, co-acts with a valve seat 22 rotatably and slidably mounted. in the flanged member15. A pin 23 projects from the side wall of the valve seat 22 into an inclined slot 24 (Fig. 1) so that, by movingthe pin along the slot, said seat can be moved to or away from the head 21 of the plug.

Similarly, a pin 25 projects from the Venturi tube 9 through a slot 26 in the easing 6 whereby the tube can be slidably adjusted as required, and a pin 27 projects from the sleeve 10 through a slot 28 in the casing to enable the sleeve, and therefore the plug 21, to be moved axially relative to the seats 12 and 22, respectively. This movement may be effected through the medium of a lever 29 pivoted, at 30, to thecarburetor casing and formed with an arcuate slot 31 into which the pin 27 projects.

As the sleeve 10 is moved away from its seat H the area of the passage between its flared end and the seat is gradually increased an amount depending on the shape of the seat of the passage while simultaneously the area between the head 21 ot the plug and the seat 22, which area is the throttle opening, is also increased by an amount depending on the shape of the bee. d. The head 21 and the seat l-il are shown parabolical but they may be conical or even straight.

In the operation of the carburetor the mixture of fuel and air formed within the passage 11 impinges on the tapered plug and is deflected outwards by the latter in conjunction with the flared part of the sleeve, whereupon it meets and is subjected to the comminuting energy of a cross stream of air entering by the openings 13 and passing at high velocity over the head 21 of the plug 20. As the sleeve 10 opened further (by moving the lever 20 in the direction of the arrow, Fig. 1) the proportion of outer air flowing through the passage 12 relative to the mixture flowing along the passage 11 is automatically increased by reason of the shape of the tube 11, seat 14 and plug head 21 to maintain a mixture of proper proportions for every degree of throttle opening.

A rich starting mixture can be obtained by simply moving back the valve seat 22. by means of the pin 23. while the sleeve 10 remains closed against its seat 1i. when all the air (100%) passes through the sleeve. hen the throttle is opened the prop rtion of air entering by the inner passage 11 through the sleeve 10 is reduced until with a full open throttle about 20% or 25% of the total air passes through the sleeve while the remaining or flows through the passage 12 round the sleeve.

The slidable Venturi tube 9 enables the richness or consistency of the mixture ot fuel and air flowing through the passage 11 in the sleeve to be varied to suit climatic and other conditions and a notable feature is that this variable mixture is fully compensated throughout the whole range of throttle opening.

The diameter of the bore of the sleeve 11 must not be too small as all or practically all the air must pass therethrough when the engine is running at low speeds. The size depends on the engine and a bore about 25% ot the total throttle opening has been found to give good results generally.

Fuel issues from the fuel nozzle 8. of which the best position is coaxial with the sleeve 10 as shown. and is atomized by the tapered plug and the meeting and mixing of the cross streams of gaseous mixture and air. The tapered wall of the plug con titutes an impinging and spreading surl'ace and the finely divided mixture issues from the sleeve 10 as a thin sheet which is cut by the cross current of outer air flowing inwards practically at right angles to the direction of flow of the gaseous: mixture. whereby thorough comminiition and ato1nization is obtained without sza'riiiciug volumetric etliciem-y.

In the modified construction ol' carburetor illustrated by Fig. 5 the chiel point of diflerence is that the tubular casing is flanged and turned inwards at its lower end to pro vide an inner open ended tube (3 into which the fuel nozzle projects and over which the sleeve 10 slides. In other respects the construction and operation 01 the carburetor is similar to that already described with retorence to Figs. 1 and l and will now be understood.

Most carburetors introduce a butterfly or equivalent valve but in view of the very low surface tension of petrol. any advantage gained by spraying hetore passing such a valve is minimized by the spra coalescing on the valve whence it. has to be drifted otl the inrushing air. It will be seen that in the carlmretors in accordance with the present invention there is no butterfly 01' similar valv. but the throttle opening is determined by the head 21. There are few parts in the carburetor and each can be readily replaced. and dust or grit cannot remain lodged on the surface of the valve seat 14. or on the head 21 owing to the high velocity of the air passing over same: further there is but one single jet which functions at all engine speeds as distinct from carburetors employing pilot jets.

Instead of the Venturi tube 0 a variable mixture may be obtained by changing the size ot. jet in fuel nozzle. or a hand controlled vari: ble needle jet may be used. The venturi is simpler, however. and is preterably made parabolical internally and with its largest dian'ieter approximately the same as the inner diameter of the casing 0 (or (if) in Fig. In any case the mixture determined by the size of the jet or needle, or venturi will be compensated for the whole range 01" throttle opening.

It will be apparent to those skilled in the art that various changes in detail may be made in the constructions of my improved spraying device as herein particularly described and illustrated without departing :lfrom the spirit or scope of the invention as hereinafter claimed.

lVhat I claim as my invention and dcsire to secure by Letters Patent is 1. A carburetor comprising a casing; means for the supply of liquid fuel opening into the said casing; an open ended tubular member slidable in the said casing over the said fuel supply means to provide an inner passage for primary gaseous mixture and an outer space for the passage of a separate supply of air; a member Within the said tubular member to serve as a throttle valve, and as an impinging and spreading surface for the said gaseous mixture passage through the said tubular member; and valve seats in the said casing for both the slidable tubular member and throttle valve.

2. A carburetor comprising a casing; means for the supply of liquid fuel openmg into the said casing; an open ended tubular member slidable in the said casing over the said fuel supply means to provide an inner passage for primary gaseous mixture and an outer space for the passage of a separate supply of air; a member Within the said tubular member to serve as a throttle valve, and as an impinging and spreading surface for the said gaseous mixture passage through the said tubular member; valve seats in the said casing for both the slidable tubular member and throttle valve; and means whereby the proportions of the liquid fuel and air constituting the primary gaseous mixture can be varied independently.

3. A carburetor comprising a casing; means for the supply of liquid fuel openiug into the said casing; an open ended tubular member slidable in the said casing over the said fuel supply means to provide an inner passage for primary gaseous mixture and an outer space for the passage of a separate supply of air; a member Within the said tubular member to serve as a throttle valve, and as an impinging and spreading surface for the said gaseous mixture passage through the said tubular member; a seat for said valve adjustable Within the said casing; means for adjusting the said seat from the exterior of said casing; a seat in the said casing for said slidable tubular member; and a Venturi sleeve slidable in said tubular member with respect to said fuel supply means for varying the proportion of fuel and air passing through the said tubular member.

4i. A carburetor com rising a casing; means for the supply of liquid fuel opening into the said casing; an open ended tubular member slidable in the said casing over the said fuel supply means to provide an inner passage for primary gaseous mixture and an outer space for the passage of a separate supply of air; a plug carried by, the flared end of the said tubular member and having a parabolical upper portion serving as a throttle valve and a conical lower portion serving as an impinging and spreading surface to direct the said gaseous mixture across the surrounding air passage; seats in said casing both for the said slidable tubular member and the said throttle valve.

5. A carburetor comprising a casing; means for the supply of liquid fuel opening into the said casing; an open ended tubular member slidable in the said casing over the said fuel supply means to provide an inner passage for primary gaseous mixture and an outer space for the passage of a separate supply of air; a plug carried by the flared end of the said tubular member and having a parabolical upper portion serving as a throttle valve and a conical lower portion serving as an impinging and spreading surface to direct the said gaseous mixture across the surrounding air passage; a seat for said valve adjustable Within the said casing; means for adjusting said seat from the exterior of the said casing; a seat in the said casing for said slidable tubular member; and means whereby the proportions of the liquid fuel and air constituting the primary gaseous mixture can be varied independently.

ture.

ARCHIBALD J ARVIE LAIRD.

In testimony whereof I aflix my signa- 

